Simplified Procedure for Estimating Seismic Displacement Capacity of Concrete Piles in Wharves

The procedure of estimating the seismic displacement capacity of piles under each performance level in current wharf practices involves monitoring the material strains specified in the design criteria during nonlinear static pushover analysis with a complex numerical model. Thus, a simplified procedure for concrete piles is proposed by developing closed-form formulas for displacement ductility capacity and yield displacement of piles, while the displacement capacity is the product of ductility capacity and yield displacement. The ductility capacity assures that the pile material strain limits specified in the criteria are not exceeded. The basic form of the formula for ductility capacity is established by using the equivalent cantilever concept to model the pile–soil interaction. Then, large quantities of moment–curvature analyses of sections and pushover analyses of concrete piles were conducted to determine the related parameters in the formula by considering numerous influencing factors. The results show that the ductility capacity can be expressed as a function of the curvature ductility capacity of pile sections at the selected performance level and parameter ψ. Based on the outcomes of curvature and pushover analyses, a set of practical formulas are proposed to determine the curvature ductility capacity, which depends on the longitudinal or transverse reinforcement ratios and axial force level, along with ψ, which depends on the aforementioned factors as well as the unsupported length of the pile.